Recently, the performance and functionality of digital cameras and digital movie cameras that use some solid-state image sensor such as a CCD and a CMOS (which will be sometimes simply referred to herein as an “image sensor”) have been enhanced to an astonishing degree. In particular, the size of a pixel structure for use in a solid-state image sensor has been further reduced these days thanks to rapid development of semiconductor device processing technologies, thus getting an even greater number of pixels and drivers integrated together in a solid-state image sensor. As a result, the resolution of an image sensor has lately increased rapidly from around one million pixels to ten million or more pixels in a matter of few years. On top of that, the quality of an image captured has also been improved significantly as well. As for display devices, on the other hand, LCD and plasma displays with a reduced depth now provide high-resolution and high-contrast images, thus realizing high performance without taking up too much space. And such video quality improvement trends are now spreading from 2D images to 3D images. In fact, 3D display devices that achieve high image quality although they require the viewer to wear a pair of polarization glasses have been developed just recently.
As for the 3D image capturing technology, a typical 3D image capture device with a simple arrangement uses an image capturing system with two cameras to capture a right-eye image and a left-eye image. According to the so-called “two-lens image capturing” technique, however, two cameras need to be used, thus increasing not only the overall size of the image capture device but also the manufacturing cost as well. To overcome such a problem, methods for capturing multiple images with parallax by using a single camera have been researched and developed. For example, Patent Document No. 1 discloses a technique for obtaining two images with parallax at the same time using color filters. FIG. 11 schematically illustrates an image capturing system that adopts such a technique. The image capturing system that uses that technique includes a lens 3, a lens diaphragm 19, a light beam confining plate 20 with two color filters 20a and 20b that have mutually different transmission wavelength ranges, and a photosensitive film 21. In this case, the color filters 20a and 20b may be filters that transmit red- and blue-based light rays, respectively.
In such an arrangement, the incoming light passes through the lens 3, the lens diaphragm 19 and the light beam confining plate 20 and produces an image on the photosensitive film 21. In the meantime, only red- and blue-based light rays are respectively transmitted through the two color filters 20a and 20b of the light beam confining plate 20. As a result, a magenta-based color image is produced on the photosensitive film by the light rays that have been transmitted through the two color filters. In this case, since the color filters 20a and 20b are arranged at mutually different positions, the image produced on the photosensitive film comes to have parallax. Thus, if a photograph is developed with the photosensitive film and viewed with a pair of glasses, in which red and blue films are attached to its right- and left-eye lenses, the viewer can view an image with depth. In this manner, according to the technique disclosed in Patent Document No. 1, images with parallax can be produced using the two color filters.
According to the technique disclosed in Patent Document No. 1, the light rays are imaged on the photosensitive film, thereby producing images with parallax there. Meanwhile, Patent Document No. 2 discloses a technique for producing images with parallax by transforming incoming light into electrical signals. FIG. 12 schematically illustrates a light beam confining plate according to such a technique. Specifically according to that technique, a light beam confining plate 22, which has a red ray transmitting R area 22R, a green ray transmitting G area 22G and a blue ray transmitting B area 22B, is arranged on a plane that intersects with the optical axis of the imaging optical system at right angles. And by getting the light rays that have been transmitted through those areas received by a color image sensor that has red-, green- and blue-ray-receiving R, G and B pixels, an image is generated based on the light rays that have been transmitted through those areas.
Patent Document No. 3 also discloses a technique for obtaining images with parallax using a similar configuration to the one illustrated in FIG. 12. FIG. 13 schematically illustrates a light beam confining plate as disclosed in Patent Document No. 3. According to that technique, by making the incoming light pass through R, G and B areas 23R, 23G and 23B of the light beam confining plate 23, images with parallax can also be produced.
According to the techniques disclosed in Patent Documents Nos. 1 to 3 mentioned above, images with parallax can be produced by arranging RGB color filters on a light beam confining plate. However, since the light beam confining plate is used, the percentage of the incoming light that can be used eventually decreases. In addition, to increase the effect of parallax, the RGB color filters should be arranged at distant positions and should have decreased areas. In that case, however, the percentage of the incoming light that can be used eventually further decreases.
Unlike these techniques, Patent Document No. 4 discloses a technique for obtaining multiple images with parallax and a normal image that is free from the light quantity problem by using a diaphragm in which RGB color filters are arranged. According to that technique, when the diaphragm is closed, only the light rays that have been transmitted through the RGB color filters are received. On the other hand, when the diaphragm is opened, the RGB color filter areas are outside of the optical path, and therefore, the incoming light can be received entirely. Consequently, images with parallax can be obtained when the diaphragm is closed and a normal image that uses the incoming light highly efficiently can be obtained when the diaphragm is opened.